The invention set forth in this specification pertains to new and improved emitters for use in connection with drip irrigation. It is primarily directed toward emitters which are responsive to the force applied by water within the interior of an enclosed space or conduit so as to accomplish a flow control function.
It is considered well known that emitters for use in drip irrigation are devices which are intended to dispense or emit comparatively small quantities of liquid from an enclosed space such as the space within the interior of a tube or conduit as and where such liquid is needed for agricultural or similar purposes. An extremely large number of different types of emitters have been constructed and used. It appears that the most desirable emitters for many types of applications are structures which are responsive to the water within such an enclosed space in the sense that they are capable of opening up so as to provide a comparatively large passage leading from the interior of such an enclosed space when substantially no water is being supplied to the interior of such a space and in the sense that they are capable of "closing up" to a degree when significant water is supplied to the interior of such a space so as to emit or dispense only a limited or restricted quantity of water.
Emitters of the type indicated in the preceding sentence are considered to be particularly advantageous in many applications because in effect they serve as flow regulators dispensing or emitting quantities of liquid in accordance with the water supplied to the interior of a tube, conduit, or the like. If properly constructed such emitters can dispense water at substantially a uniform rate regardless of the flow and water conditions within the interior of a tube, conduit, or similar structure. Further, when water conditions within an enclosed space or even adjacent to such an emitter are such that the emitter is essentially open, contaminants which might cause mal-performance of other types of emitters can flow into and through the emitter so as to be dispensed from it.
An understanding of the invention is not considered to require or necessitate a detailed discussion of all of the known emitters which are responsive to the water within a pipe, conduit, or the like, so as to dispense a regulated or controlled flow of water. The present invention is directed toward improving flow regulating emitters which are constructed so as to utilize an elongated tubular member which is adapted to be deformed or flexed in accordance with the water supply within a pipe, conduit, or related enclosure. A device of this type is shown in FIG. 8 of the Whear U.S. Pat. No. 3,512,363, entitled "MOISTURE DISTRIBUTION SYSTEM". This device is described in the specification of this patent as consisting of a drainage tube.
It is understood that devices as are illustrated in this FIG. 8 of this patent have been primarily utilized as valves in draining tubes or the like. It is understood that such devices as are commercially manufactured consist of short lengths of an extruded tube of a flexible, resilient material which have been deformed slightly through the application of heat along lines transverse to their axes so as to facilitate their being flexed in response to applied force of moving water so as to close off their interiors. When water is no longer applied to such devices so as to cause them to close off, the inherent properties of the material in such devices causes them to revert to their initial configurations, allowing water to drain through them.
Such a drainage tube can be utilized as an emitter by carefully controlling the water conditions within a pipe, conduit or related enclosure so that such a tube does not completely close off as it is contacted by water, but instead deforms or flexes in response to the applied water within a pipe, conduit or the like so that the passage through the tube varies in dimension in accordance with variations in the water contacting the tube. As this occurs the variation in the size of the passage causes the tube to act as a flow regulator such that the amount of water passing through the tube does not vary to any significant extent as there is variation in the water flow within the interior of the pipe or conduit.
The use of these drainage tubes as are described in the noted Whear patent as emitters is not considered desirable because of the degree of control of applied water which is necessary to utilize such a drainage tube as a satisfactory emitter. Such control is necessary because the performance of such a drainage tube--either as a drainage tube or as an emitter--will be related to a number of factors. An important one of these factors is the temperature of the water used in connection with such a tube. There is always a danger that when such a tube is used as an emitter that it will be inadvertently and/or undesirably "operated" by the applied water so that such a tube will unintentionally completely pinch or close off or will dispense a greater quantity of water than desired.